A device for the mechanical stimulation of body parts with damaged bones is suggested in the Article "Controlled Mechanical Stimulation in the Treatment of Tibial Fractures" by J. Kenwright, et al. Clin. Orthop. and Related Research, Vol. 241, pp. 3647, 1989.
It is also known from European Patent No. 450,423 (Clasbrummel) that certain parts of the body can be held in an external immobilization device and that a lesion area can thus be treated with stimulating, rhythmic, back-and-forth motions at a certain stimulational amplitude. Here the mechanical energy is supplied more-or-less directly to the fracture gap by means of a drive acting on the external immobilization device.
Devices for producing focussed shock waves are known from U.S. Pat. No. 2,559,227.
Shock waves are acoustic waves with a frequency spectrum ranging from audible frequencies to the ultrasonic (100 MHz). They are usually generated in water and conducted into the body of a human being or animal through a certain volume of water. Shock waves are known from various applications for the crushing of body concretions and from uses involving the induction and stimulation of bone growth. W. German Patent No. 2,351,247 and U.S. Pat. No. 4,905,671 are two such disclosures.
Shock waves can be produced by various technical generation processes; for example, the electrohydraulic process uses a spark discharge to generate the underwater shock waves. An elliptical metal reflector is used to focus the shock waves. The spherical underwater shock wave generated at the first focal point by spark discharge with an electrode is transmitted to and focussed at the second focal point of the semi-ellipsoid by reflection from the ellipsoid wall. For the purpose of therapy, imaging processes such as ultrasound or audiograph are used as a location aid so that the tissue to be treated can be made to coincide with this focus as discussed in U.S. Pat. No. 2,559,227. Another method by which shock waves can be produced and focussed is that based on the electromagnetic principle, according to which the shock wave is produced by a flat membrane and possibly focussed by means of an acoustic lens as shown in European Patent No. 183,236.
A second electromagnetic principle makes use of a cylindrical source in which case focussing is accomplished by means of a parabolic reflector disclosed in German Patent No. 4,036,981.
According to yet another principle of generation, the shock waves are produced by piezoceramic elements on a self-focusing spherical shell, taught by West German Patent No. 4,000,362.